Ctrl+M (interactive mirror) is not taking the object's rotation into account
Not sure if this is what you need, but if you use Collection instance.
-Create a new collection, add the object there
-Right Click on the collection &gt; Instance
-Then right click on the viewport &gt; Mirror &gt;X Global

Also, you can add more object to that collection and it's going to have a mirror object automatically


I made a video using this technique for an animation here: https://vimeo.com/417302896 or here (same one) https://youtu.be/deIwRZt-U80
Around minute 3:04.
Hope that helps